Previous mouse studies have shown that targeting the blood vessels of fat tissue (or white adipose) reduced a third of their body weight. White adipose just under our skin stores fat and provides us with insulation.

But because many drugs fail in the transition between rodents and primates, the team set out to demonstrate in monkeys the weight-loss effects seen in mice.

The drug selectively binds to a protein on the surface of fat-supporting blood vessels and kills those cells within blood vessels of adipose tissue. (It’s like starving a tumor by cutting off the blood vessels that supply it.) Without blood supply, fat cells are reabsorbed and metabolized.

In 10 rhesus monkeys, one month of treatment resulted in:

Rapid weight loss. Up to 15% of their body weight.

Reduced body fat. MRIs scans show that the treated monkeys shed 38.7% of body fat on average. Pictured, monkey before and after (red is fat).

Slimmer abdominal circumference (waistline). Up to 14%.

Improved insulin resistance, which makes them at lower risk for type 2 diabetes and cardiovascular disease.

The monkeys remained bright and alert throughout, interacting with caretakers and demonstrating no signs of nausea or food avoidance. Though, side effects included increased amounts of urine and slight dehydration, both symptoms of mild kidney failure.

Janet Fang has written for Nature, Discover and the Point Reyes Light. She is currently a lab technician at Lamont-Doherty Earth Observatory. She holds degrees from the University of California, Berkeley and Columbia University. She is based in New York.
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